1. Field of the Invention
The present invention relates to an image processing device having forgery preventing function for preventing unauthorized reproduction of specified images regarding which duplication is forbidden, such as paper currency.
2. Description of the Related Art
A so-called color photocopier such as shown in FIG. 1 is known as a system for digital reading images of color originals and generating duplicate images.
In FIG. 1, an image scanner unit 1001 reads the original images and performs digital signal processing. Also, a printer unit 1002 performs full-color printer output of an image corresponding to the original image read by the image scanner 1001 on recording paper.
At the image scanner 1001, an original 1004 placed between a pressing plate 1000 having an original pressing face which has been subjected to mirror finishing and an original table glass 1003 is irradiated by the light of a lamp 1005. The reflected light from the original 1004 is guided to mirrors 1006, 1007, and 1008, and forms an image on a 3-line solid-state imaging device (hereafter referred to as “CCD”) 1010 by a lens 1009. The three image signals red (R), green (G), and blue (B), output from the CCD 1010 are sent to a signal processing unit 1011. Here, the lamp 1005 and mirror 1006 are mechanically moved at a speed V in a perpendicular direction as to the electric scanning (main scanning) direction of the CCD 1010, and the mirrors 1007 and 1008 at a speed V/2, thereby scanning the entire surface of the original 1004 (sub-scanning). The image on the original 1004 is read at a resolution of 400 dpi in both main scanning and sub-scanning.
The signal processing unit 1011 electrically processes the input image signals so as to divide into the components of magenta (M), cyan (C), yellow (Y), and black (K), and sends CMYK image signals to the printer unit 1002. One color component of M, C, Y, and K, is sent to the printer unit 1002 for each time the original is scanned by the image scanner 1001, so one printout is completed by the original being scanned a total of four times.
At the printer unit 1002, the C, M, Y, or K image signals input from the image scanner unit 1001 are sent to a laser driver 1012. The laser driver 1012 performs modulation driving of a semiconductor laser device 1013 according to the input image signals. The laser beam output from the semiconductor laser device 1013 scans over a photosensitive drum 1017 via a polygon mirror 1014, f-θ lens 1015, and mirror 1016, so as to form a 400 dpi electrostatic latent image on the photosensitive drum 1017 for the main scan and sub-scan.
A rotating developer 1018 is configured of the magenta developing unit 1019, a cyan developing unit 1020, a yellow developing unit 1021, and a black developing unit 1022, with the four developing units alternately coming into contact with the photosensitive drum 1017, thereby developing the electrostatic latent image formed on the photosensitive drum 1017 with toner. A transfer drum 1023 has recording paper, supplied from recording sheet cassettes 1024 or 1025, wrapped thereupon, and the toner image formed on the photosensitive drum 1017 is transferred onto the recording paper.
Thus, the four color toner images of M, C, Y, and K, are sequentially transferred on the recording paper, following which the recording paper passes through a fixing unit 1026, and the recording paper with toner fixed thereupon is discharged out of the apparatus.
As described in U.S. Pat. Nos. 5,321,470, 5,216,724, 5,633,952, 5,430,525, 5,227,871, etc., with a color photocopier of such a configuration, the signal processing unit 1011 is arranged such that image signals representing an original image are analyzed, judgement is made regarding whether or not there are specified original images regarding which duplication is forbidden, such as paper currency (hereafter referred to as “specified original judging”), and in the event that judgement is made that a specified original image exists therein, the image output from the printer unit 1002 is filled in such that correct duplication result cannot be obtained, by substituting the image signals sent to the printer unit 1002 with, for example, a predetermined value that is not dependent on the original image, or the like. As described above, the configuration shown in FIG. 1 reads the original image four times repeatedly, so acts of forgery can be prevented before they occur, by, for example, performing the specified original judging at the time of reading the first time, and formation of the M color component latent image, in parallel, so in the event that judgement is obtained that a specified original image does exist, the laser driving signals (image signals) of the subsequent C, Y, and K color components are substituted with a predetermined value, thereby coloring the entire output image practically black.
With the above-described color photocopier, there is basically the need for the image scanner unit 1001 which reads original images and the printer unit 1002 which outputs photocopied images, to operate synchronously. That is to say, the RGB image signals output from the CCD 1010 are processed at the signal processing unit 1011 one pixel at a time and converted into CMYK image signals, sent to the printer unit 1002 sequentially, and form an electrostatic latent image on the photosensitive drum 1017. Image formation is performed for one of the color components M, C, Y, and K, the image formation process is repeated for each of the color component, and original image reading is performed four times consecutively. Accordingly, the image output at the end can be colored in so long as the specified original judgment is performed by at least the third scan of the four scans.
Also, with the above-described color photocopier configuration, the image scanner unit 1001 and the printer unit 1002 need to operate at the same time. For example, in the event that the fixing unit 1026 is a normal thermal fixing type, and the heater is not sufficiently heated, the printer unit 1002 will go into standby, so photocopying and image reading cannot be performed.
In the event of photocopying multiple copies of an original image with the configuration of the above-described color photocopier, there is the need to read the image multiple times according to the multiple copies to be output. Further, in the event that there are multiple originals, the originals need to each be read multiple times, so the time required for photocopying color originals is great.
Now, there is a configuration wherein page memory for storing at least one page worth of color image that has been read is provided in the image scanner unit 1001, and the photocopy images output by reading out the image from the page memory four times repeatedly, thereby enabling multiple outputs with reading the image only one time. With such a configuration, reading the image just one time is sufficient even in the event of outputting multiple copies of the original, so the time required for photocopying color originals can be reduced.
In the event that the image scanner unit 1001 has page memory, the specified original judging is performed during one original scan in parallel with reading of the image. At the point that judgement is made that there is a specified original image, the image is already stored in the page memory. Accordingly, in the event that this image is read out of the page memory by some sort of means, this consequently permits photocopying of the specified original. Of course, a configuration could be made wherein that image output is colored in with a predetermined value at the point that judgement is made that the specified original exists. However, normally, with configurations having page memory, image reading and image output are performed asynchronously, so that apparatus may be out putting an image completely unrelated with this while scanning the original containing the specified original image. In this case, another image output which is not the image to be colored in, will be colored in.
Also, an arrangement may be conceived wherein the image stored in the page memory can be deleted at the point that judgement is made that a specified original image exists. However, with this arrangement, no image output corresponding to the read image is performed at all, so there is no record that an unauthorized act was committed, which is undesirable in operating the apparatus.